1. Field of the Invention
This invention relates generally to an apparatus for mixing fluent material, including slurries, which are liquids mixed with particulate matter such as gravel, sand, dust, mortar and cement.
2. Description of the Related Art
On a typical construction site, mortar and/or concrete is utilized in different stages of the operation from laying block to pouring walls and sidewalks. Having an apparatus on site that mixes the fluent mortar or concrete slurry is essential. A mixing apparatus is used to mix the necessary ingredients to create the mortar or concrete mixture. The laborers fill the mixing apparatus with mortar or cement and sand and other essential ingredients, such as water, and the mixing blades mechanically stir the materials, thereby creating a slurry of water, dissolved chemicals and particulate. The slurry is then either poured into another apparatus for transport throughout the site or poured directly into the designated concrete form.
In conventional mixers, the charge height, which is the height at which the mixer is filled, and the dump height, which is the height at which the fluent material is dumped, are substantially different, and the charge height is higher than the dump height. For example, the Essick mixing device sold by Multiquip, Inc. of Carson, Calif., has a dump height that is substantially lower than the charge height. Having a dump height that is lower than the charge height may seem reasonable, but there are ergonomic disadvantages with this configuration. Conventional mixers having a higher charge height require an operator to lift bags of mortar or cement and shovel sand and gravel to chest height. The repetitive nature of this action may cause back strain, fatigue or injury to the operator, making him less effective and possibly causing delay at the job site.
It is also important in conventional mixers to maintain a low center of gravity for the apparatus during dumping so that the apparatus does not become unbalanced and tip over. The Multiquip, Inc.'s mixer maintains a low center of gravity by pivoting the hopper around the mixing paddle axis to pour its contents. The hopper is rotated and the lip of the hopper is gradually moved to a position below the upper surface of the contents of the hopper. There is not a significant change in the position of the center of gravity of this mixing apparatus because of the minimal or non-existent movement of the hopper's center of gravity relative to the paddle axis. The slender frame of the mixer can withstand this movement, and therefore it will not tip over.
Additionally, it is common to have a wheeled support frame on the mixer. This allows for towing of the mixing device to different job sites. The mixer produced by Multiquip, Inc., has two wheels at the rear of the device and a foot at the front. The wheels position the bottom of the drum higher above the ground for clearance when towing. This again raises the height at which the materials are to be installed (charge height).
There is also a greater risk of theft with a mixer that is wheeled, since any person could enter the job site and hitch the wheeled mixer to a vehicle and leave.
Therefore, there is a need for an improved mixing apparatus.